1. Field of the Invention
The present invention relates to scanning probe microscopy, and more specifically, it relates to techniques for controlling the orientation and morphology of carbon nanotubes, which have many uses, e.g., as probe tips for scanning probe microscopes.
2. Description of Related Art
One method for fabricating conventional scanning probe microscope (SPM) probes uses standard lithographic techniques and materials. The probes made by this method typically have a pyramidal tip shape and are fabricated from silicon. Some more specialized SPM probes are the etch sharpened conventional silicon probe and the adhesive or electrically fused attached carbon nanotube probes, directly grown nanotube probes and amorphous carbon spike probes.
The techniques and materials as defined by standard lithographic processes limit conventional probes. The materials typically used are silicon or silicon nitride. These materials are hard but brittle and can chip and wear relatively easily. The lithographic techniques as well as the materials limit the aspect ratio of these conventional probes. Lithographic techniques have a lower limit on feature size making it difficult to make high aspect ratio probes and more importantly the brittle material will break easily if the aspect ratio is too high such as with etch sharpened conventional probes or focused ion beam milled conventional probes.
The more specialized carbon nanotube tips take advantage of some of the useful properties of the carbon nanotube but the attachment or growth techniques have little control over shape and alignment of the nanotube. Amorphous carbon spike probes do not have the robust nature of carbon nanotubes and can break more easily.